To generate a stable reference voltage over process, voltage, and/or temperature (“PVT”) variations in today's electronics, a bandgap reference voltage generator is used for such electronics. Additionally, a startup circuit is necessary to make sure a bandgap reference voltage generator will work properly when the bandgap reference generator is connected to a power supply during startup. For instance, if the power supply has a slow rise time at low temperature and slow corner process, the startup may not occur in the bandgap reference voltage generator due to low current beta characteristics of bipolar transistors at low temperature conditions.
Some bandgap reference voltage generators can provide assistance for startup operations using a startup circuit. However, these bandgap reference voltage generators usually have several major drawbacks. Some conventional bandgap reference voltage generators cannot provide a fast-enough startup. Additionally, the bandgap reference voltage generators are overly complicated and power consuming, and do not do well with low supply voltages. Furthermore, startup circuits in such bandgap references voltage generators are highly reliant on the supply voltage VDD to determine an operation for the respective startup circuit. Another drawback is that the startup circuit undesirably affects the respective bandgap reference voltage generator even after startup has completed.
Therefore, it is desirable to provide improved methods, systems, and circuits for bandgap reference voltage generation that can reduce the various drawbacks.